Dynamic bias for a power amplifier

ABSTRACT

A dynamic bias controller dynamically biases a plurality of amplifiers residing in a power amplifier. Based upon a communication signal amplitude, the dynamic bias controller turns off (removes bias from) selected amplifiers when the communication device is to transmit a low power communication signal, and turns on (applies bias to) selected amplifiers when the communication device is to transmit a higher power communication signal. A plurality of dynamic bias controllers may control a plurality of amplifiers such that a plurality of communication signal strengths can be realized. Another embodiment employs a dynamic bias controller to control at least one prematching impedance network coupled to the selected amplifier, thereby adjusting the system impedance to a desired value.

BACKGROUND OF THE INVENTION

1. Technical Field

The invention is generally related to power amplifiers and, moreparticularly, is related to controlling bias current of a poweramplifier.

2. Related Art

With the increasing power efficiency demands from users of mobilecommunication devices, such as cell phones and the like, mobilecommunication device manufacturers are continually searching for ways toimprove power consumption efficiency within the mobile communicationdevice, thereby increasing the useful operating period that a mobilecommunication device gets from a single charge of the power source, suchas, but not limited to, a battery or fuel cell. During a normal voiceconversation by a person using the mobile communication device, thetransmitting function consumes a very large amount of available power.As such, energy conservation in transmitters is of paramount importance.

Conventional mobile communication devices typically consume largeamounts of power as a voice signal is converted into a communicationsignal and amplified to a power level necessary for transmission fromthe mobile communication device to a base station. Within thecommunication industry, significant efforts continue to attempt tominimize power consumption. Therefore, there is an ongoing need tocontinue to reduce energy consumption in mobile communication devices.

SUMMARY

The invention provides for dynamically biasing a plurality of amplifiersresiding in a power amplifier. One embodiment employs at least onedynamic bias controller. Based upon the amplitude of a communicationsignal, such as a radio frequency (RF) signal, the dynamic biascontroller deactivates (turns off) selected amplifiers (remove bias)when the communication device is to transmit a low power communicationsignal, and activates (turns on) the selected amplifiers (apply bias)when the communication device is to transmit a higher powercommunication signal. A plurality of dynamic bias controllers maycontrol a plurality of amplifiers such that a plurality of communicationsignal strengths can be realized.

In the one embodiment, the dynamic bias controller may employ anattenuator that attenuates the detected communication signal. Thoseportions of the detected communication signal that are at least equal tothe predetermined amplitude that are not attenuated, are rectified by arectifying circuit. A low pass filter filters out AC componentsresulting in a base band signal that actuates a transistor residing in aswitch. When the transistor is activated (turned on), an emitterfollower transistor generates a control signal that activates a selectedpower amplifier.

Another embodiment further incorporates a prematching impedance network.The prematching impedance network is coupled to the selected poweramplifier controlled by the dynamic bias controller. When the selectedpower amplifier is activated (turned on) by the dynamic bias controller,the prematching impedance network adjusts the system impedance to adesired value. When the selected power amplifier is deactivated (turnedoff) by the dynamic bias controller, the prematching impedance networkadjusts the system impedance to another desired value. The prematchingimpedance network may be coupled to the input or the output of theselected power amplifier. Alternatively, two prematching impedancenetworks could be employed, one connected to the input and the otherconnected to the output of the selected power amplifier. Furthermore,the prematching impedance network may be further controlled by thedynamic bias controller such that switches couple and decouple theprematching impedance network from the mobile communication devicecircuitry.

Other systems, methods, features and advantages of the invention will beor will become apparent to one with skill in the art upon examination ofthe following figures and detailed description. It is intended that allsuch additional systems, methods, features and advantages be includedwithin this description, be within the scope of the invention, and beprotected by the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The components in the figures are not necessarily to scale, emphasisinstead being placed upon illustrating the principles of the invention.In the figures, like reference numerals designate corresponding partsthroughout the different views.

FIG. 1 is a simplified block diagram of a mobile communication devicecommunicating with a base station.

FIG. 2 is a block diagram illustrating selected transmitter componentsof the mobile communication device of FIG. 1.

FIG. 3 is a block diagram of the dynamic bias controller residing in themobile communication device of FIG. 1.

FIG. 4 is a block diagram showing components residing in an embodimentof the dynamic bias controller of FIG. 3.

FIG. 5 is a block diagram showing selected components of an exemplaryembodiment of the dynamic bias controller of FIG. 4.

FIG. 6 is a graph of the output power of the power amplifiers of FIG. 3when controlled by the dynamic bias controller of FIGS. 3 and 4.

FIG. 7 is a block diagram of an embodiment of the dynamic biascontroller having alternative configurations of the rectifying circuitand reference voltage generator.

FIG. 8 is a block diagram of an embodiment of a dynamic bias controllercontrolling a plurality of second power amplifiers in a multiple stagepower amplifier.

FIG. 9 is a block diagram of an embodiment of a dynamic bias controllercontrolling a plurality of power amplifiers residing in a single-stage,multiple power amplifier unit.

FIG. 10 is a block diagram of an embodiment of the dynamic biascontroller controlling a second stage amplifier and a prematchingimpedance network.

DETAILED DESCRIPTION

FIG. 1 is a simplified block diagram of a mobile communication device100 communicating with a base station 102. Mobile communication device100 typically has a microphone 104, a speaker 106, a transmit/receiveunit 108 and an antenna 110. To initiate a voice conversation, a useractuates keys 112 on a keypad to transmit a destination code, such as atelephone number, to the transmit/receive unit 108. The user's voice istransformed into a communication signal by the transmit/receive unit 108and transmitted to power amplifier 116 via connection 118. Poweramplifier 116, using energy from power source 120, amplifies thecommunication signal and injects the communication signal onto antenna110 via connection 122. The amplified communication signal 124 is thentransmitted to base station antenna 126, typically set up on a tower 128or other similarly situated high point. Non-limiting examples of powersource 120 include conventional batteries, fuel cells and solar energypanels. The received communication signal 126 then travels to the basestation receiver/transmitter 130 via connection 132. Once the basestation 102 has established connectivity to the destination location(not shown), as defined by the telephone number, a person using mobilecommunication device 100 carries on a voice telephone conversation withanother person at the destination location.

FIG. 2 is a block diagram illustrating additional selected transmittercomponents of the mobile communication device 100. The transmit/receiveunit 202, in this simplified illustrative example, has at least aprocessor 204, a transmit unit 206 and a power amplifier bias controller208. Single-stage power amplifier unit 210 employs first stage 212having two power amplifiers 214 and 216 that amplifies communicationsignals received from transmit unit 206 via connection 218 (see alsoFIG. 1). The transmit/receive unit 202 and the power amplifier 210 arewell known components of a conventional mobile communication device 100.Detailed operation of the individual components are not described indetail other than to the extent necessary to understand the operationand functioning of these components with respect to the invention. Oneskilled in the art will realize that the mobile communication device 100or other similar mobile communicators may have the components shown inFIG. 2 connected in a different order and manner than shown in FIG. 2,or may not include all of the components shown in FIG. 2, or may includeadditional components connected in some manner with the components shownin FIG. 2. Any such variations in a mobile communication device 100 or asimilar mobile communication device are intended to be within the scopeof this disclosure.

The single-stage power amplifier unit 210 as shown in FIG. 2 is asimplified illustration of a power amplifier. In one embodiment, poweramplifier 210 employs a first power amplifier 214 and a second poweramplifier 216. An input matching impedance and coupler 220 is disposedbetween the input to the power amplifier 210 (at connection 218) and thepower amplifiers 214 and 216. An output matching impedance and coupler222 is disposed between the power amplifiers 214 and 216. Acommunication signal is received by power amplifier 210 from thetransmit unit 206 via connection 218. The communication signal travelsthrough the input matching impedance and coupler 220 to the poweramplifiers 214 and 216 via connections 224 and 226, respectively. Afteramplification by the power amplifiers 214 and 216, the communicationsignal is transmitted to the output matching impedance and coupler 222,via connections 228 and 230, respectively. The amplified communicationsignal is transmitted from the output matching impedance and coupler222, via connection 122, to antenna 110. Typically, there may be othercomponents between antenna 110 and output matching impedance 222, butsuch components are not described here for convenience and because suchcomponents are not relevant to the explanation of the operation andfunctionality of the single-stage power amplifier unit 210 and itscomponents. The degree of amplification of the communication signal bythe first power amplifier 214 and the second power amplifier 216 isdetermined by processor 204 and controlled by the power amplifier biascontroller 208 residing in the transmit/receive unit 202.

Processor 204 communicates with the transmit unit 206, via connection231, to specify various parameters associated with the converted outputcommunication signal. For example, the processor 204 may specify thetransmission frequencies to be used by the transmit unit 206 when avoice signal is converted to a communication signal suitable fortransmission. Processor 204 also controls the amplification levels ofthe power amplifiers 214 and 216 by providing instructions to the poweramplifier bias controller 208, via connection 232. The power amplifierbias controller 208 controls the bias of the first power amplifier 214,via connection 234, thereby controlling the amount of signalamplification by the first power amplifier 214.

For illustrative purposes, FIG. 2 shows the bias of the second poweramplifier 216 controlled by power amplifier bias controller 208, viaconnection 236. This configuration corresponds to a typical conventionalsystem in that the power amplifier bias controller 208 controls theamount of signal amplification by the second power amplifier 216.

FIG. 3 is a block diagram of the dynamic bias controller 302 residing inthe mobile communication device 300. The dynamic bias controller 302controls the bias applied to the second stage power amplifier 216, viaconnection 304. The dynamic bias controller 302 detects the RF signal onconnection 218, via connection 306, and activates the second stage poweramplifier 216 when the amplitude of the RF signal is such that both thefirst stage power amplifier 214 and the second stage power amplifier 216are to be used by the single-stage power amplifier unit 308 to generatethe amplified communication signal. Alternatively, dynamic biascontroller 302 may detect the RF signal on any other suitable connection(not shown) having a signal having a voltage that is spectrally relatedto the signal on connection 218.

FIG. 4 is a block diagram showing components residing in an embodimentof the dynamic bias controller 302. These components include at leastattenuator 402, DC stop 406, rectifying circuit 408, low pass filter410, switch 412, reference voltage generator 414 and emitter followertransistor 416. Dynamic bias controller 302, via connection 306, detectsthe communication signal. Attenuator 402 attenuates the detectedcommunication signal such that portions of the communication signal thatexceed a predefined threshold are output by attenuator 402, viaconnection 418. Thus, any portion of the communication signal that isoutput over connection 418 corresponds to an operating condition wherethe second stage power amplifier 216 (FIG. 3) should be amplifying thecommunication signal. Attenuator 402 may be implemented using well knowncomponents commonly employed in attenuator and thresholding systems.Thus, a detailed description of the individual components residing inattenuator 402 is not provided since such a description is not necessaryto understand the operation and functioning of the dynamic biascontroller 302. One skilled in the art will realize that attenuator 402may be implemented by a variety of means such that portions of thecommunication signal that have an amplitude that exceed the predefinedthreshold is output by the attenuator 402. Any such embodiments ofattenuator 402 utilized in a dynamic bias controller 302 are intended tobe within the scope of this disclosure and to be protected by theaccompanying claims.

The output of attenuator 402 is coupled to the DC stop 406 viaconnection 418. DC stop 406 prevents any direct current (DC) generatedwithin the dynamic bias controller 302 from flowing out of the dynamicbias controller 302 via connection 306. Such DC currents, if allowed toflow out of the dynamic bias controller 302 over connection 306, mightundesirably interfere with the communication signal being detected bythe single-stage power amplifier unit 308 (FIG. 3). Since DC stop 406may be implemented using well known components, such as a capacitor orany other device that is designed to stop the flow of DC current, adetailed description of the individual components residing in DC stop406 is not provided. All such embodiments of DC stop 406 utilized in adynamic bias controller 302 are intended to be within the scope of thisdisclosure and to be protected by the accompanying claims.

Rectifying circuit 408 detects portions of the communication signal thatexceeds the predefined threshold. Rectifying circuit 408 rectifies theportions of the communication signal received, and outputs the rectifiedportions of the communication signal to low pass filter 410, viaconnection 422. Low pass filter 410 filters out any fundamental andharmonic frequency components, such as, but not limited to, alternatingcurrent (AC) components, of the detected portions of the communicationsignal received over connection 422 and outputs the base band portion ofthe communication signals to switch 412, via connection 430. Switch 412,via connection 432, controls emitter follower 416. If base band portionsof the communication signal that exceed the predefined threshold areoutput by low pass filter 410 onto connection 430, switch 412 activatesemitter follower transistor 416, in a manner described below, such thatthe second stage power amplifier 216 (FIG. 3) is conducting. If low passfilter 410 does not output any base band signal over connection 430 (theamplitude of the detected communication signal on connection 306 isbelow the threshold of attenuator 402), then switch 412 deactivatesemitter follower transistor 416 such that the second stage poweramplifier 216 is not conducting. Reference voltage generator 414, viaconnection 434 provides an appropriate predefined voltage reference suchthat switch 412 can control emitter follower transistor 416.

FIG. 5 is a block diagram showing selected components of an exemplaryembodiment of the dynamic bias controller 302 (FIGS. 3 and 4). Oneskilled in the art will appreciate that the illustrated components asshown in FIG. 5 may have the elements connected in a different order andmanner than shown in FIG. 5, or may not include all of the elementsshown in the components of FIG. 5, or may include additional elementswithin the components connected in some alternative manner. Any suchvariations in the elements of the components residing in a dynamic biascontroller 302 that have the same operation and functionality of theillustrative components shown in FIG. 5 are intended to be within thescope of this disclosure and to be protected by the accompanying claims.

Rectifying circuit 408 of FIG. 5 includes a reference resistor (R_(REF))502, a first transistor (Q1) 504, a second transistor (Q2) 506 and aresistor connected to ground (R_(M)) 508. R_(REF) 502 is shown coupledto a reference voltage (V_(REF)) such that a reference current (I_(REF))is provided to transistors Q1 504 and Q2 506 as shown. Transistor Q2 506is coupled to Vcc, via connection 510, as illustrated. For convenienceof illustration, Vcc is shown to be available from a bus 512 that iseasily accessible by other components of the dynamic bias controller 302and other components (not shown) residing in the mobile communicationdevice 300 (FIG. 3). As portions of the communication signal that have amagnitude exceeding the predefined threshold are received by therectifying circuit 408 on connection 418, are rectified and then passedto the low pass filter 410 over connection 422.

Low pass filter 410 includes a filtering resistor (R_(F)) 514 and afiltering capacitor (C_(F)) 516. The rectified portions of thecommunication signal exceeding the threshold are attenuated by R_(F)514. Then, at node 518, the AC components of the portions of the RFsignals are filtered by C_(F) 516. After filtering by low pass filter410, a signal is delivered to switch 412 via connection 430. The signalon connection 430 includes those portions of the communication signalhaving an amplitude that exceeds the predefined threshold, as defined byattenuator 402 (FIG. 4), that have been rectified by the rectifyingcircuit 408 and that have had the AC components filtered by low passfilter 410.

Switch 412 includes a switching transistor (Q3) 520 and a switchresistor (R_(S)) 522 connected to ground. If any signal is provided toswitch 412 over connection 430, as described above, Q3 is activated. Ifthere is no signal on connection 430 (i.e., the amplitude of thecommunication signal is less than the threshold as determined byattenuator 402) then Q3 is deactivated.

Reference voltage generator 414 includes a first diode (D1) 524, asecond diode (D2) 526 and a resistor (R_(G)) 528. Reference voltagegenerator 414 is coupled to a voltage source (Vcc) on bus 512 viaconnection 530, and is coupled to switch 412 via connection 434. When Q3520 is conducting, the voltage on connection 432 is small andinsufficient to activate Q4 532. When Q3 520 is not conducting, voltageon connection 432 is equal to the voltage generated by voltage generator414 and is sufficient to activate Q4 532. Diodes D1 and D2 may be anysuitable conventional diode or a specially fabricated diode.

Emitter follower transistor 416 includes a transistor (Q4) 532 and aresistor (R_(EF)) 534. Q4 is connected to the voltage source Vcc at bus512 via connection 536 as shown. When the voltage on connection 432 issubstantially zero, Q4 is activated (not conducting) and the voltage atnode 538 is zero. When the voltage on connection 432 is equal to thevoltage provided by reference voltage generator 414 (Q3 520 is notconducting) then Q4 532 is activated (conducting). When Q4 is activated,current flows from bus 512 through Q4 532 and through R_(EF) 534 toground. Thus, the voltage at node 538 is now equal to (I_(EF)×R_(EF)).This non-zero voltage at node 538 is output from the emitter followertransistor 416 via connection 304. As described above, when the voltageon connection 304 is above the turn-on voltage, the second stage poweramplifier 216 (FIG. 3) is activated such that the communication signalis amplified by the second stage power amplifier 216. One skilled in theart will appreciate that the transistor Q4 532 and the resistor R_(EF)534 can be sized so that a desired voltage is provided on connection 304and so that the second stage power amplifier 216 is activated.

In summary, the dynamic bias controller 302 (FIGS. 3 and 4) senses theamplitude of a communication signal and automatically determines whenthe second stage power amplifier 216 residing in the single-stageamplifier 212 is to be activated, thereby amplifying the communicationsignal that is to be transmitted from the mobile communication device300 (FIG. 3). The dynamic bias controller 302 accomplishes this functionby detecting those portions of the communication signal that have anamplitude greater than a predefined threshold value, as determined byattenuator 402 (FIG. 4), and by generating a voltage on connection 304that activates the second stage power amplifier 216.

FIG. 6 is a graph of the output power of the power amplifiers 214 and216 (FIG. 3) when controlled by the dynamic bias controller 302 (FIGS. 3and 4). The vertical axis of graph 600 is the output bias current, inper unit (p.u.), of the first stage power amp 214 and the second stagepower amp 216 (FIG. 3). The horizontal axis of graph 600 is theamplitude, in milli-decibels (dBm), of the detected communication signalon connection 306 (FIGS. 3 and 4). The output of amplifiers 214 and 216,as shown on graph 600, are intended to be illustrative hypotheticaloutputs of the amplifiers 214 and 216 to facilitate an explanation ofthe operation and functionality of the dynamic bias controller 302 inresponse to a detected hypothetical communication signal. Thus, oneskilled in the art will appreciate that the output of the two amplifiersin practice can be specified, designed and/or implemented in mobilecommunication device 300 (FIG. 3) in a manner that provides any desiredoutput level from the two power amplifiers 214 and 216.

Curve 602 represents an example of the output of the first stage poweramp 214. Curve 604 represents the power output of the second stage poweramp 216. When the communication signal amplitude detected on connection306 is between −10 dBm and 10 dBm, the output of the second stage poweramp 216 is zero p.u. That is, the dynamic bias controller 302 hasdeactivated the second stage power amp 216 when the amplitude of thecommunication signal is between −10 dBm and 10 dBm. When thecommunication signal amplitude is between −10 dBm and 10 dBm, only thefirst stage power amp 214 is required to be activated to provide anadequate amplified communication signal to the antenna 110 (FIG. 1).Since second stage power amp 216 is deactivated, power is conserved.

When the amplitude of the communication signal reaches 10 dBm, theturn-on point 606 of the second stage power amp 216 is reached and thesecond stage power amp 216 activates. The output of the second stagepower amp 216 increases in a manner that corresponds to the increasingamplitude of the communication signal such that an amplifiedcommunication signal of adequate strength for broadcasting is deliveredto antenna 110. In the simplified illustrative example of FIG. 6, theturn-on point 606 is selected to be at a communication signal amplitudeequal to 10 dBm. This 10 dBm turn-on point 606 was effected by thethreshold point as defined by the attenuator 402 (FIG. 4). When theamplitude of the communication signal exceeds 10 dBm, a portion of thecommunication signal is processed by the dynamic bias controller 302such that the output of the dynamic bias controller 302 on connection304 activates the second stage power amp 216.

The 10 dBm turn-on point 606 illustrated in the graph 600 of FIG. 6 wasselected as a convenience for explaining the operation and functionalityof a dynamic bias controller 302 implemented in a mobile communicationdevice 300 (FIG. 3). The turn-on point 606 could be designed to be atany value of the communication signal amplitude depending upon theparticular needs of the mobile communication device 300. The turn-onpoint 606 can be specified by the appropriate determination of thevarious components of the dynamic bias controller 302. For example, thethreshold of attenuator 402 could be modified. Alternatively, V_(REF) inthe rectifying circuit 408 (FIG. 5) and/or the reference resistorR_(REF) 502 could be selected such that the turn-on point 606 could beadjusted to a different value. Additionally, the turn-on voltage oftransistor Q3 520 residing in switch 412 could be specified such thatthe turn-on point 606 could be adjusted. One skilled in the art willappreciate that other components residing in the dynamic bias controller302 might be defined in a similar manner to adjust the turn-on point606. Any such variations in the components residing in the dynamic biascontroller 302, and/or any variations in the elements residing in thosecomponents, are intended to be within the scope of this disclosure andto be protected by the accompanying claims.

FIG. 7 is a block diagram of an embodiment of the dynamic biascontroller 700 having an alternative configuration of the rectifyingcircuit 702 and reference voltage circuit 704. Generally, when comparedto the configuration of the components residing in the dynamic biascontroller 302 of FIG. 5, the components of the dynamic bias controller700 are generally similar. Low pass filter 410, switch 412 and emitterfollower transistor 416, are substantially the same as in the embodimentas shown in FIG. 5. Furthermore, the individual components are coupledtogether in substantially the same manner. That is, rectifying circuit702 is coupled to the low pass filter 410 via connection 422. Low passfilter 410 is coupled to switch 412 via connection 430. Switch 412 iscoupled to emitter follower transistor 416 via connection 432. Theemitter follower is coupled to the voltage source Vcc via connection 536and the output of the emitter follower transistor 416 is output atconnection 304.

Rectifying circuit 702 employs different elements as compared to therectifying circuit 408 in FIG. 5. Here, a rectifying circuit 702 employsa first transistor (Q5) 706, a second transistor (Q6) 708 and areference resistor (R_(REF1)) 710. R_(REF1) is coupled to a referencevoltage V_(REF) via connection 712. Reference voltage circuit 704 isalso coupled to the same V_(REF) via connection 714. Reference voltagecircuit 704 includes a transistor (Q7) 716, a transistor (Q8) 718, areference resistor (R_(REF2)) 720 and a resistor (R_(G)) 722 connectedto ground. Here, R_(REF1) 710 and R_(REF2) 720 have been selected suchthat corresponding reference currents, I_(REF1) and I_(REF2) areprovided to the rectifying circuit 702 and the reference voltage circuit704, respectively. The dynamic bias controller 700 operates insubstantially the same manner as explained above for the dynamic biascontroller 302 illustrated in FIG. 5. Here, an attenuator (not shown)employs a predefined threshold to define the turn-on point of thedynamic bias controller 700. Rectifying circuit 702 rectifies thoseportions of the communication signal greater than the predefinedthreshold, low pass filter 410 filters out the AC components of theportions of the communication signal rectified by rectifying circuit702, and the output of low pass filter 410 activates the switch 412 whenportions of the rectified/filtered communication signal are present ordeactivates the switch when the rectified/filtered portions of thesignal are absent. Similar to the embodiment according to FIG. 5, theemitter follower transistor 416 will either activate or deactivateaccording to the status of switch 412.

FIG. 8 is a block diagram of an embodiment of a dynamic bias controller802 controlling a plurality of second power amplifiers 804, 806 and 808residing in a multiple stage power amplifier unit 810. Multiple stagepower amplifier unit 810 employs three stages; N−1 stage 812, N^(th)stage 814 and N+1 stage 816. A first power amplifier (amp) 818 residesin each stage 812, 814 and 816. Typically, a multiple stage poweramplifier unit 810 employs a plurality of impedance matching and couplercircuits 820. The communication signal enters the multiple stage poweramplifier unit 810 on connection 822 and is amplified to a desiredamplified communication signal and output to antenna 110 via connection122.

Dynamic bias controller 802 senses the communication signal onconnection 826. When the amplitude of the communication signal is lessthan the turn-on point, the multi-stage power amplifier unit 810amplifies the communication signal with only the plurality of firstpower amplifiers 818 residing in the three stages 812, 814 and 816. Whenthe amplitude of the communication signal exceeds the turn-on point, thedynamic bias controller 802 activates each of the second poweramplifiers 804, 806 and 808 via connection 824.

One skilled in the art will realize that each of the impedance matchingand coupler circuits 820 of FIG. 8 are likely to have different elementsresiding in each circuit 820, and that FIG. 8 is intended to be asimplified illustration of the manner in that components might becoupled in a multiple stage power amplifier unit. Thus, variations inthe components of a multiple stage power amplifier unit 810 employingthe dynamic bias controller 802 may vary from one specific applicationto another without substantially affecting the operation andfunctionality of the dynamic bias controller 802 that is activating ordeactivating the second power amplifiers 804.

The multiple stage power amplifier 810 illustrated in FIG. 8 employsthree amplification stages 812, 814 and 816 for convenience ofillustration purposes. The dynamic bias controller 802 could equally beapplicable to a multiple stage power amplifier unit having only twoamplification stages, or a multiple stage power amplifier units havingmore than three amplification stages. One aspect of the invention is theability of the dynamic bias controller 802 to enable the control of aplurality of second power amplifiers based upon a single turn-on point.

For convenience of illustration, the plurality of second poweramplifiers 804, 806 and 808 are shown controlled by a single connection824. Alternatively, each of the plurality of second power amplifiers804, 806 and 808 could be controlled over an individual connection (notshown) without departing substantially from the operation andfunctionality of the dynamic bias controller 802. Individual connectionswould be applicable if multiple stage power amplifier unit 810 employsdifferent rated second power amplifiers (804, 806 and/or 808), eachhaving a different turn-on signal requirement. In this situation, thedynamic bias controller 802 would have a means for providing therequired unique turn-on signal to each of the second power amplifiers.For example, additional components could be added to the dynamic biascontroller 802 such that the required signal is uniquely provided toeach of the second power amps 804, 806 and 808 via the individualconnections.

FIG. 9 is a block diagram of an embodiment of a dynamic bias controller902 controlling a plurality of power amplifiers 904 and 906 residing ina single-stage, multiple power amplifier unit 908. With thesingle-stage, multiple power amplifier unit 908, a communication signalis provided on connection 910. The amplified communication signal isoutput to antenna 110 over connection 122. Matching impedance andcoupler circuits 912 may be employed for the plurality of poweramplifiers 904, 906 and 914. For convenience of illustration, thesingle-stage multiple power amplifier unit 910 is illustrated havingthree power amplifiers, a first power amplifier 914, a second poweramplifier 904 and an N^(th) power amplifier 906. Dynamic bias controller902 controls the second power amplifier 904 via connection 916. Dynamicbias controller 902 controls the N^(th) power amplifier 906 viaconnection 918.

The communication signal is detected by the dynamic bias controller 902on connection 920. When the amplitude of the communication signal isbelow the first turn-on point, dynamic bias controller 902 deactivatesthe second power amplifier 904 and the N^(th) power amplifier 906. Withthis operating condition, the communication signal is amplified only bythe first power amplifier 914.

When the amplitude of the communication signal exceeds a first turn-onpoint, the dynamic bias controller 902 activates the second poweramplifier 906. The communication signal is then amplified by the firstpower amplifier 914 and the second power amplifier 904. (For thisoperating condition, it is assumed that the amplitude of thecommunication signal is less than a second turn-on point, as describedbelow.)

When the amplitude of the communication signal exceeds a second turn-onpoint, the dynamic bias controller 902 activates the N^(th) poweramplifier 904. Thus, the communication signal being amplified by thesingle-stage, multiple power amplifier unit 908, is amplified by ailthree power amplifiers 914, 904 and 906 during this operating condition.

Alternatively, the dynamic bias controller 902 may have deactivated thesecond power amplifier 904 in conjunction with the activation of theN^(th) power amplifier 906, assuming that the N^(th) power amplifier 906was larger than the second power amplifier 904. Then, at a third turn-onpoint, the dynamic bias controller 902 could activate the second poweramplifier 904. Furthermore, an optional connection 922 could have beenprovided to control the first power amplifier 914. A plurality ofturn-on points could be defined within the dynamic bias controller 902such that any one or any combination of the power amplifiers 914, 904and 906 could be activated depending on a particular amplitude of thecommunication signal. Thus, a hand-held communication device (not shown)employing a single-stage, multiple power amplifier unit 908 with thedynamic bias controller 902, could be designed to operate in a highlyefficient manner, thus conserving the limited power supply andoptimizing operation time of the mobile communication device.

The dynamic bias controller 902 can easily be designed to control fouror more such power amplifiers (not shown). However, the single-stage,multiple power amplifier unit 908 having three power amplifiers 914, 904and 906 is used to explain the functionality and operation of theembodiment of the dynamic bias controller 902.

Yet another alternative embodiment of the dynamic bias controller mayhave fewer components than the dynamic bias controller 302 (FIGS. 3 and4) or 700 (FIG. 7). For example, in some applications the emitterfollower transistor 416 (FIG. 7) may be omitted. The transistor Q3 520residing in switch 412 may be configured such that the output of switch412 alone, over connection 432, is sufficient to control a poweramplifier. Alternatively, the reference voltage circuit 704 may not berequired. A suitable voltage could be provided from another component(not shown) residing in the mobile communication device 300 (FIG. 3).Another alternative embodiment of a dynamic bias controller couldprovide a control signal (turn-on/turn-off) to a power amplifier thatalready has its own controller switch. All such alternative embodimentsof a dynamic bias controller are intended to be within the scope of thisdisclosure and be protected by the accompanying claims.

Another embodiment of a dynamic bias controller system is shown in FIG.10. FIG. 10 is a block diagram of an embodiment of the dynamic biascontroller 302 controlling a second stage amplifier 216 and aprematching impedance network 1002 employed in a mobile communicationdevice 1000. One skilled in the art will appreciate that systemperformance may be optimized by having an output matching impedance andcoupler 1004, which is optimized for an operating condition where onlythe first stage power amplifier 214 is operating (second stage poweramplifier 216 is off). System performance could be further optimized ifthe output matching impedance is modified when both the first stagepower amplifier 214 and the second stage power amplifier 216 areoperating.

When the second stage power amplifier 216 is controlled by the dynamicbias controller 302, a prematching impedance network 1002, coupledbetween the second stage power amplifier 216 and the output matchingimpedance and coupler 1004 (FIG. 10), can be used to modify the outputimpedance when both the first stage power amplifier 214 and the secondstage power amplifier 216 are operating. When the dynamic biascontroller 302 has deactivated the second stage power amplifier 216, theprematching impedance network 1002 does not affect the output matchingimpedance because no power flows from the second stage power amplifier216, through the prematching impedance network 1002, to the outputmatching impedance and coupler 1004.

When the dynamic bias controller 302 has activated the second stagepower amplifier 216, the prematching impedance networks 1002 and 1012match the output matching impedance because power flows from the secondstage power amplifier 216, over connection 1006, through the prematchingimpedance network 1002, over connection 1008, to the output matchingimpedance and coupler 1004.

In another embodiment, dynamic bias controller 302 may be coupled to theprematching impedance network 1002 with connection 1010. Dynamic biascontroller 302 could provide an auxiliary signal, via connection 1010,to one or more switches (not shown) residing in or coupled toprematching impedance network 1002. When the dynamic bias controller 302has deactivated the second stage power amplifier 216, the one or moreswitches are actuated by dynamic bias controller 302 to isolate theprematching impedance network 1002 such that the output matchingimpedance is not affected. When the dynamic bias controller 302 hasactivated the second stage power amplifier 216, the one or more switchesare actuated by dynamic bias controller 302 to couple the prematchingimpedance network 1002 such that the output matching impedance isaffected.

Prematching impedance network 1002, and any associated switches, may beimplemented using well known components commonly employed in matchingimpedance systems and switching systems. Thus, a detailed description ofthe individual components residing in prematching impedance network 1002or any associated switches are not described since such a description isnot necessary to understand the operation and function of the dynamicbias controller 302. One skilled in the art will realize that theprematching impedance networks 1002 and 1012, and associated switches,may be implemented by a variety of means such that the output matchingimpedance is adjusted to a desired value when the dynamic biascontroller 302 has activated the second stage power amplifier 216. Allsuch embodiments of prematching impedance network 1002 utilized with adynamic bias controller 302 are intended to be within the scope of thisdisclosure and to be protected by the accompanying claims.

Alternatively, the prematching impedance network 1012 could be coupledto the input of the second stage power amplifier 216 as illustrated inFIG. 10. Also, the dynamic bias controller 302 could be coupled to theprematching impedance network 1012, via connection 1014, such thatswitches (not shown) residing in prematching impedance network 1012 areactuated to uncouple and recouple the prematching impedance network 1012in a manner similar to that described above for the prematchingimpedance network 1002.

Yet another embodiment may employ two prematching impedance networks1002 and 1012. The prematching impedance networks 1002 and 1012 may alsoemploy switches (not shown) controlled by the dynamic bias controller302 as described above.

Furthermore, prematching impedance network 1002 and/or prematchingimpedance network 1012 may be coupled to the output and/or the input,respectively, of the first stage power amplifier 214 and controlled asdescribed above. Prematching impedance network 1002 is coupled to theoutput of the first stage power amplifier 214 at a convenient locationon connection 228. Similarly, prematching impedance network 1012 iscoupled to the input of the first stage power amplifier 214 at aconvenient location on connection 1016.

Up to four prematching impedance networks could be employed in asingle-stage power amplifier unit 308. A prematching impedance networkcould be coupled to the input and/or the output of either, or both, thefirst stage power amplifier 214 and the second stage power amplifier216. Dynamic bias controller 302 provides the appropriate controlsignals to the first stage power amplifier 214 and/or the second stagepower amplifier 216, and to any of the prematching impedance networksemployed in the single-stage power amplifier unit 308.

For convenience of explaining the operation and functionality of thevarious embodiments of the dynamic bias controller illustrated in FIGS.3-10, the communication signal detected by the dynamic bias controllerwas illustrated and described as being received from transmit unit 206(FIG. 3). However, the dynamic bias controller 302 (and alternativeembodiments of the dynamic bias controller) operates satisfactorily whenthe communication signal is provided from any of the components (notshown) residing in the mobile communication device 300 (FIG. 3). Thedynamic bias controller requires only that the delivered communicationsignal have a sufficient bandwidth as to provide meaningful detection ofamplitude and a meaningful specification of the operating turn-onpoint(s). Depending upon the particular mobile communication device 300in which a dynamic bias controller is installed, the dynamic biascontroller has elements defined such that the delivered communicationsignal can be adequately detected such that the appropriateturn-on/turn-off signals can be delivered to the power amplifiers. Allsuch variations in the source of the communication signal delivered to adynamic bias controller and the associated components (and theirelements) are intended to be within the scope of this disclosure and tobe protected by the accompanying claims.

Furthermore, for convenience of illustration and the explanation of theoperation and function of a dynamic bias controller, the components(attenuator 402, DC stop 406, rectifying circuit 408, low pass filer410, switch 412, reference voltage generator 414 and the emitterfollower transistor 416) are shown residing in the dynamic biascontroller 302 (see FIG. 4). Alternatively, these components may residein other convenient locations outside of the dynamic bias controller 302without adversely affecting the operation and functionality of thedynamic bias controller 302. Also, the necessary reference voltages andsupply voltages Vcc could be provided from any convenient locationwithin the mobile communication device 300 and at any convenient value.All such alternative embodiments of the dynamic bias controller areintended to be within the scope of this disclosure and to be protectedby the accompanying claims.

While various embodiments of the invention have been described, it willbe apparent to those of ordinary skill in the art that many moreembodiments and implementations are possible that are within the scopeof this invention.

What is claimed:
 1. A system that controls power amplifiers, comprising:a bias controller for outputting a control signal, the bias controllercoupled to a node in a communication device such that a communicationsignal is sensed; a first power amplifier configured to amplify thecommunication signal; a second power amplifier configured to amplify thecommunication signal and responsive to the control signal, such that thebias controller activates the second power amplifier when an amplitudeof the communication signal is at least equal to a predeterminedamplitude, and such that the bias controller deactivates the secondpower amplifier when the amplitude of the communication signal is lessthan the predetermined amplitude; and a coupler coupled to the firstpower amplifier and the second power amplifier such that a firstamplified communication signal output by the first amplifier and asecond amplified communication signal output by the second amplifier arecombined.
 2. The system of claim 1, wherein the second power amplifierdetects the communication signal and outputs an amplified communicationsignal when the control signal activates the power amplifier.
 3. Thesystem of claim 1, further comprising a plurality of amplifiers coupledto the bias controller and responsive to the control signal such thatthe bias controller activates each one of the plurality of poweramplifiers when the amplitude of the communication signal is at leastequal to the predetermined amplitude, and such that the bias controllerdeactivates each one of the plurality of power amplifiers when theamplitude of the communication signal is less than the predeterminedamplitude.
 4. The system of claim 1, further comprising a mobilecommunication device, in which the bias controller, the first poweramplifier and the second power amplifier reside.
 5. A system thatcontrols at least one power amplifier, comprising: a bias controller foroutputting a control signal; a power amplifier responsive to the controlsignal; a threshold detector configured to output a portion of adetected communication signal that is at least equal to a predeterminedamplitude, and such that the threshold detector outputs no signal whenthe amplitude of the detected communication signal is less than thepredetermined amplitude; and a switch for providing the control signalfrom the bias controller to the power amplifier, such that when anoutput of the threshold detector is the portion of the detectedcommunication signal that is at least equal to the predeterminedamplitude the switch is actuated to a first state such that the controlsignal activates the power amplifier, and such that when the thresholddetector outputs no signal the switch is actuated to a second state suchthat the control signal is not provided and the power amplifierdeactivates.
 6. The system of claim 5, wherein the threshold detector isan attenuator, the attenuator attenuating to zero the portions of thedetected communication signal that are less than the predeterminedamplitude.
 7. The system of claim 5, wherein the bias controller furthercomprises: a rectifying circuit coupled to the threshold detector; a lowpass filter coupled between the rectifying circuit and the switch; and atransistor residing in the switch and coupled to the low pass filter,such that portions of the detected communication signal at least equalto the predetermined amplitude are input to the rectifying circuit andrectified into a rectified signal, and such that the rectified signal isinput to the low pass filter wherein alternating current (AC) componentsof the rectified signal are filtered out and a direct current (DC)filtered signal is output, and such that the DC filtered signalactivates the transistor, thereby generating the control signal thatactivates the power amplifier.
 8. The system of claim 5, wherein thebias controller further comprises a reference voltage generator coupledto the switch such that the control signal equals a preselectedreference value when the switch in the first state, and such that thecontrol signal is substantially zero when the switch is in the secondstate.
 9. The system of claim 5, wherein the bias controller furthercomprises an emitter follower coupled to the switch and generates anamplified control signal such that the amplified control signal issuitable for activating the power amplifier when the switch is in thefirst state, and such that the amplified control signal is suitable fordeactivating the power amplifier when the switch is in the second state.10. The system of claim 5, wherein the bias controller further comprisesan emitter follower coupled to the switch and generates an amplifiedcontrol signal such that the amplified control signal is suitable foractivating the power amplifier when the switch is in the first state,and such that the amplified control signal is suitable for deactivatingthe power amplifier when the switch is in the second state.
 11. Thesystem of claim 10, such that when the amplitude of the communicationsignal is less than one of the unique predetermined amplitudes thecorresponding power amplifier is deactivated.
 12. The system of claim 5,further comprising: a plurality of power amplifiers responsive to thecontrol signal; a plurality of threshold detectors, each of theplurality of threshold detectors uniquely associated with one of theplurality of power amplifiers, and configured to output a signal whenthe detected communication signal is at least equal to a uniquepredetermined amplitude; and a plurality of switches, each of theplurality of switches uniquely associated with one of the plurality ofpower amplifiers and the associated threshold detector, each one of theplurality of switches configured to receive the signal from thecorresponding threshold detector, and further configured to provide thecontrol signal to the associated power amplifier in response toreceiving the signal from the corresponding threshold detector, suchthat the associated power amplifier is activated only when the detectedcommunication signal is at least equal to the corresponding uniquepredetermined amplitude.
 13. A system that controls power amplifiers,comprising: a bias controller for outputting a control signal, the biascontroller coupled to a node in a communication device such that acommunication signal is sensed; a power amplifier responsive to thecontrol signal, such that the bias controller activates the poweramplifier when an amplitude of the communication signal is at leastequal to a predetermined amplitude, and such that the bias controllerdeactivates the power amplifier when the amplitude of the communicationsignal is less than the predetermined amplitude; and a prematchingimpedance element coupled to the power amplifier such that when the biascontroller activates the power amplifier the prematching impedanceelement adjusts a system impedance to a first value, and such that whenthe bias controller deactivates the power amplifier the prematchingimpedance element adjusts the system impedance to second value.
 14. Thesystem of claim 13, wherein the prematching impedance element is coupledto an output of the power amplifier.
 15. The system of claim 13, whereinthe prematching impedance element is coupled to an input of the poweramplifier.
 16. The system of claim 13, wherein the prematching impedanceelement is coupled to the bias controller such that the prematchingimpedance is decoupled when the bias controller deactivates the poweramplifier, and such that the prematching impedance is recoupled when thebias controller activates the power amplifier.
 17. The system of claim16, further comprising at least one switch residing in the prematchingimpedance element, wherein the prematching impedance element switch isactuated such that the prematching impedance is decoupled when the biascontroller deactivates the power amplifier, and wherein the prematchingimpedance element switch is actuated such that the prematching impedanceis recoupled when the bias controller activates the power amplifier. 18.A system for controlling power amplifiers, comprising: means fordetecting a communication signal; means for activating a first poweramplifier when the communication signal is detected; means for detectingan amplitude of the communication signal; means for generating a controlsignal in a first state when the amplitude of the communication signalis less than a predetermined amplitude; means for generating the controlsignal in a second state when the amplitude of the communication signalis at least equal to the predetermined amplitude; means for providingthe control signal to a second power amplifier; means for activating thesecond power amplifier when the control signal is in the first state;means for deactivating the second power amplifier when the controlsignal is in the second state; and means for coupling an output of thefirst power amplifier to an output of the second power amplifier. 19.The system of claim 18, further comprising means for coupling aprematching impedance to the output of the second power amplifier suchthat the prematching impedance element adjusts a system impedance to afirst value when the second power amplifier is activated and such thatthe prematching impedance element adjusts the system impedance to asecond value when the second power amplifier is deactivated.
 20. Thesystem of claim 18, further comprising: means for generating a pluralityof unique control signals, each one of the plurality of unique controlsignals being associated with a plurality of unique predeterminedamplitudes; and means for providing the plurality of unique controlsignals to a plurality of power amplifiers such that each one of theplurality of unique control signals activates one of the plurality ofpower amplifiers when the amplitude of the communication signal is atleast equal to one of the unique predetermined amplitudes.
 21. A methodfor controlling power amplifiers, the method comprising the steps of:activating a first power amplifier when a communication signal isdetected; detecting an amplitude of the communication signal; generatinga control signal in a first state when the amplitude of thecommunication signal is less than a predetermined amplitude; generatingthe control signal in a second state when the amplitude of thecommunication signal is at least equal to the predetermined amplitude;providing the control signal to a second power amplifier; deactivatingthe second power amplifier when the control signal is in the firststate; activating the second power amplifier when the control signal isin the second state; and combining an output of the first poweramplifier with an output of the second power amplifier via a couplerthat couples an output connection of the first power amplifier with anoutput connection of the second power amplifier.
 22. The method of claim21, further comprising the steps of: adjusting a prematching impedanceto the second power amplifier such that the prematching impedanceelement adjusts a system impedance to a first value when the secondpower amplifier is activated; and adjusting the prematching impedancesuch that the prematching impedance element adjusts the system impedanceto a second value when the second power amplifier is deactivated. 23.The method of claim 21, further comprising the steps of: generating aplurality of unique control signals, each one of the plurality of uniquecontrol signals being associated with a plurality of uniquepredetermined amplitudes; and providing the plurality of unique controlsignals to a plurality of power amplifiers such that each one of theplurality of unique control signals controls one of the plurality ofpower amplifiers, such that when the amplitude of the communicationsignal is at least equal to one of the unique predetermined amplitudesthe corresponding power amplifier is activated.
 24. The method of claim21, further comprising the steps of: adjusting a prematching impedancecoupled to the output of the second power amplifier to a first valuewhen the second power amplifier is activated; and adjusting theprematching impedance to a second value when the second power amplifieris deactivated.